Multiferroics are materials that exhibit more than one of the primary ferroic properties, i.e., ferromagnetism, ferroelectricity, and ferroelasticity, in the same phase. Multiferroic 2D materials have potential for high-density multistate data storage applications, but are challenging to realize experimentally.

Mingwen Zhao and colleagues, Shandong University, Jinan, China, have used Monte Carlo simulations and density functional theory (DFT) calculations to study monolayers of VOCl₂ as a potential multiferroic 2D material. VOCl₂ monolayers can easily be stripped from the bulk material. The team found that ferroelectricity and antiferromagnetism may coexist in monolayer VOCl_2.

According to the calculations, the material has an intrinsic in-plane spontaneous electric polarization of about 300 pC m^–1, a stable antiferromagnetism with a Néel temperature of 177 K, and an energy barrier of 0.18 eV between two ferroelectric states. The ferroelectric effects are thought to be caused by off-center vanadium ions that show pseudo-Jahn-Teller distortions. The interaction between the magnetic properties and electronic polarization in the material could make it possible to tune the ferroelectricity using a magnetic field. According to the researchers, VOCl₂ monolayers are promising for use in nanoscale memory devices.

• Intrinsic multiferroicity in two-dimensional VOCl₂ monolayers,
  Haoqiang Ai, Xiaohan Song, Siyun Qi, Weifeng Li, Mingwen Zhao,
  Nanoscale 2019.
  https://doi.org/10.1039/c8nr08270g